The answer to the question “What causes osteoporosis?” can be as simple, or as complicated, as you wish to make it. I’ve cut out the fluff and provided you with the key changes that take place in your bones which lead to osteoporosis. If you can remember just 3 simple facts, you will be on your way to being an osteoporosis expert!
Fact #1: Your Bones Are An Active Organ!
Bones are an active organ that undergo a constant renewal process known as bone remodeling. Much like remodeling the living room when your furniture wears out, your bones constantly replace old and damaged regions with new, healthy bone. Two bone cells are responsible for this process. 
Fact #2: Communication Is Key!
All successful relationships thrive on good communication, and your bones are no different! The process of old bone being broken down and new bone being created is like a well-orchestrated dance. The osteoblast cells “talk” to osteoclast cells, which allows the osteoclasts to know when to break down old bone, and when to stop. Two chemical messages are used for this communication.
Fact #3: Maintaining Bone Balance Can Be Difficult!
In a perfect world, communication between your bone cells would remain flawless and the rate of bone being broken down would be perfectly matched by new bone production. For the first 20-25 years of your life, this is exactly what happens! At this point, you reach peak bone mass, or the point where your bones are at their maximum strength.
Unfortunately, communication goes awry as you age and the speed that your bones are broken down starts to exceed your body’s ability to replace it. This leads to a loss of bone density and strength over time. Bone breakdown after age 25 may be slow if you were blessed with excellent genetics and you take all of the necessary steps to prevent osteoporosis. However, it may be fast if you have a family history of osteoporosis, if you make poor lifestyle decisions, or if you have a known risk factor for accelerated bone loss including certain medications and diseases.